1. Field of Invention
This invention relates to methods and apparatus for the treatment of water and in particular to treatment of water for both domestic and industrial applications.
2. Brief Statement of the Prior Art
Municipal and industrial waters contain objectionable impurities, commonly referred to as hardness, which cause processing problems such as corrosion, scaling, etc. The scale which is formed is a calcite which has a hexagonal crystalline structure and which adheres to almost any surface such as pipes, boilers, heaters, cooling towers, shower walls, glass, sinks, etc. The scale forms more rapidly when water is heated and thus is particularly troublesome in water heaters and hot water systems by reducing heat transfer efficiency in heaters and clogging hot water pipes. Because the scale is extremely hard, it rapidly wears out faucets, valves, and pumps.
A method which has been developed for treatment of the waters comprises passing the water over an electrolytic cell containing magnesium anodes and copper cathodes. This treatment dissolves magnesium in the water and raises the pH of the water, resulting in removal of temporary hardness of the water and the formation of soft or flocculent aragonite precipitates of calcium. These precipitates are soft, non-adhesive. Water which has been treated in this method also dissolves previous deposits of calcite scale from pipes and equipment. Because the magnesium is provided as an anode, the system is electrolytically protected against corrosion. Additionally, the treatment removes or reduces the dissolved oxygen in the water, which also reduces the corrosivity of the treated water.
This treatment has been known for some time, e.g., see U.S. Pat. No. 3,342,712. Attempts to develop an efficient method and apparatus for practicing the method have, heretofore, found only limited success. Despite all the advantages this treatment offers, it has not, heretofore, found widespread acceptance because of the difficulties experienced in practicing the treatment.
The effective processing of water over a magnesium and copper electrolytic cell requires techniques to prevent polarization of the electrode surfaces and efficient removal of the soft, aragonite precipitates which are formed from the calcium in the water. Electrode assemblies of alternating, stacked magnesium and copper plates, separated by thin spacers have been used in an attempt to provide extended electrode surfaces that resist polarization. Conventional filters and sand and gravel beds have been used also to facilitate removal of the soft aragonite precipitates from the treated water. While these techniques have improved the treatment over that accomplished with the apparatus disclosed in the aforementioned patent, a highly efficient method which requires minimal maintenance has not previously been achieved.